A conventional mechanically-driven zigzag sewing machine is provided with a pattern selection dial for selecting one of a plurality of utility patterns such as a straight pattern and a zigzag pattern; and a plurality of needle swinging cams and a plurality of feed cams corresponding to the plurality of utility patterns. In the aforementioned zigzag sewing machine, when a desired pattern is selected by manually rotating the pattern selection dial, a contact respectively contacts the needle swinging cam and a feed cam that correspond to the selected pattern. Thus, applicable needle swinging movement and the cloth feed movement are executed so that the desired utility pattern is formed on the workpiece cloth.
Recently, various types of sewing machines capable of sewing a super pattern by cyclically executing a backward cloth feed (reverse feed) within a sequence forward cloth feed (normal feed) have been suggested. One example of the super pattern is a smocking pattern.
Such sewing machines are provided, for example, with a feed generating device as described below. That is, the feed generating device is provided with a plurality of zigzag feed cams controlling a feed amount of the utility pattern; two super feed cams to control a feed amount of the super pattern; and a single feed follower contacting either one of the feed cams. The aforementioned zigzag feed cams and the super feed cams are stacked in the rotational shaft direction. Additionally, a feed releasing mechanism is provided so that whenever the feed cams are switched in response to the operation of the pattern selection dial, the feed follower is released from the previously selected feed cam and the utility pattern or the super pattern currently selected by the pattern selection dial can be sewn.
The above-described feed generating device is disclosed on pages 5 to 10, FIGS. 2 to 7 of the Japanese Unexamined Patent Publication 2000-167273.
However, the above feed generating device is provided with two super feed cams thereby requiring a large arrangement space. Also, since additional space is required for the feed releasing mechanism, the overall size of the feed generating device is increased.
Furthermore, the force required for manually operating the pattern selection dial increases in proportion to the increase in the number of feed cams thereby deteriorating the operability. Therefore, provision of an operation dial for selecting the super pattern apart from the pattern selection dial can be conceived so that operability of the pattern selection dial can be improved by decreasing the number of selectable patterns by the pattern selection dial. However, in such a case, a feed releasing mechanism operating in conjunction with the super pattern operation dial would be required, which is another problem.